In recent years, Hypertext Transfer Protocols (HTTP) for streaming have become the de-facto standard for distribution of live and video-on-demand content over the Internet.
Peer-to-Peer live streaming (PLS) enables improving distribution efficiency for a given online live broadcast by having viewers of content contribute with their resources, namely bandwidth, to other viewers. Previous work in this area has proposed systems such as PPlive, CoolStreaming, T-bone, and more recently Bittorrent live. Peer-to-Peer (P2P) overlay construction for such applications falls mainly into two classes: tree-based and mesh-based systems. Although a consensus has not been reached on the best approach, mesh-based approaches have lately become more popular as they are more robust to peer churn, while tree-based overlays are more cumbersome to maintain in the same condition.
There is a recent trend of using HTTP-live streaming instead of the traditional Real Time Streaming Protocol/Real-time Transport Protocol (RTSP/RTP) for broadcast of live video content over the Internet. HTTP-live streaming consists of a set of protocols which all utilize the HTTP for transport. HTTP-live streaming changes the way a producer of the content (i.e. the streaming server) and a consumer of the content (i.e. the media player) interact.
Traditional streaming protocols such as the RTSP/RTP are based on a push-based model, where the player requests a certain stream and then the server pushes content over User Datagram Protocol (UDP) to the player controlling the speed of the delivery. HTTP-live streaming protocols are instead based on a pull-model, where it is the player that requests pieces of content over HTTP at the pace it deems suitable. On top of that, the HTTP-live protocols have been designed to support adaptive bitrate mode of operation, which avails the stream in a number of qualities. The choice of which quality to retrieve/reproduce is left to the player.
All major actors in the online broadcasting business have developed technologies which embrace HTTP-streaming and the concept of adaptive bitrate switching as a main approach for broadcasting. HTTP live has been adopted by content services and creators with support across all platforms and operating systems, including computers, tablets and smart phones. The shift from the push-based RTSP/RTP protocol to the pull-based HTTP-live protocols has rendered many of the established assumptions made in the current state-of-the art PLS obsolete. For all practical purposes, any new PLS algorithm, irrespective of its theoretical soundness, will not be deployable if it does not take into account the realities of the mainstream broadcasting ecosystem around it. Currently, both the Content Delivery Networks (CDNs) and the live streaming solution vendors are focusing on HTTP-based solutions.